The present invention relates generally to ad-hoc, multi-hop, wireless networks and, more particularly, to systems and methods for selecting antennas for transmission and reception at nodes in such networks.
Wireless data communication is often required in an environment where communications infrastructure, such as base stations or a wired backbone network, does not exist or is uneconomical or impractical to use. For example, in military or emergency environments, adequate infrastructure often does not exist in necessary locations and constructing such an infrastructure would be either impractical or uneconomical for the short-term use that is often required. Mobile multi-hop wireless networks have, therefore, been developed to provide wireless data communications in such environments.
In a conventional mobile wireless multi-hop network, each wireless node acts as a packet router that relays packets to other nodes in the network over an air interface link without routing the packets through any portion of a conventional cellular network, such as the wired backbone network, base station controllers, or base stations. Each wireless node, however, is limited in the distance over which it can reliably transmit, with transmission ranges of between a few feet and hundreds of feet being typical. Therefore, in communication environments that span large areas or have significant radio interference, packets transmitted from a sending node must often be hopped over multiple nodes in the wireless network to reach a destination. For such a multi-hop wireless network to perform effectively, all nodes must, therefore, be prepared to route packets on behalf of other nodes.
Conventionally, wireless ad-hoc networks employ omni-directional antennas for sending and receiving routed packet data. Use of omni-directional antennas, however, has the drawback that spatial re-use of the shared frequency space is limited. This limited spatial re-use results in lower throughput and higher latencies that reduces the performance of ad-hoc networks.
Therefore, there exists a need for systems and methods that can increase the spatial re-use of the shared frequency space associated with wireless, ad-hoc, wireless networks.
Systems and methods consistent with the present invention address this and other needs by implementing directional antennas in nodes of an ad-hoc, multi-hop, wireless network. Consistent with the present invention, directional antennas, such as, for example, switched beam or steered beam types of directional antennas, may be used for transmitting and/or receiving packets. Location determining techniques, such as, for example, using Global Positioning System (GPS) signals, may be employed to determine locations of nodes in the network. The determined locations may be used as a basis for selecting an appropriate antenna of multiple directional antennas for transmitting and/or receiving data to/from other nodes in the ad-hoc network. Use of directional antennas, consistent with the present invention, permits the effective division of the shared frequency space into smaller regions, thus, increasing spatial re-use in the network. Increasing the spatial re-use results in higher throughput and lower latencies in the network, as compared to exclusive use of omni-directional antennas.
In accordance with the purpose of the invention as embodied and broadly described herein, a method of selecting an antenna for transmitting data in an ad-hoc wireless network includes receiving a first message from a node in the ad-hoc wireless network, where the message includes location data associated with the node. The method further includes selecting an antenna from multiple antennas based on the location data, and transmitting a second message to the node via the selected antenna.
In a further implementation consistent with the present invention, a method for selecting a transmit antenna in a wireless network including multiple nodes is provided. The method includes receiving a message from a first node of the multiple nodes, where the message includes location data associated with the first node. The method further includes determining an angle from a second node of the multiple nodes to the first node, based on the location data, to produce a determined angle. The method also includes selecting an antenna from multiple antennas for transmitting data to the first node based on the determined angle.
In an additional implementation consistent with the present invention, a method of notifying other nodes in an ad-hoc multi-hop wireless network of a first node""s location is provided. The method includes determining a current heading and current location of the first node. The method further includes determining whether the current heading of the first node differs from a previous heading of the first node. The method also includes sending at least one message to the other nodes, based on whether the first node""s current heading differs from the previous heading, the at least one message comprising information identifying the current location of the first node.
In yet another implementation consistent with the present invention, a method of determining a heading to a first node in an ad-hoc wireless network includes receiving a message from the first node, where the message includes an identifier associated with the first node and data indicating a location of the first node. The method further includes determining a heading of the first node relative to a second node, based on the location of the first node, to produce a determined heading. The method also includes storing the identifier and determined heading in an entry of a data table.